01Cursor spotlight

<main class="stage">
  <button class="spot is-demo" type="button"><span class="spot__label">See pricing</span></button>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 변형은 이 세 줄만 바꾼다
$duration: $dur-loop;
$easing:   $ease-out;
$color:    $subject-blue;

// 커스텀 속성을 등록해야 브라우저가 퍼센트로 보간한다. 등록 안 하면 0% → 100% 로 튄다
@property --mx {
  syntax: "<percentage>";
  inherits: true;
  initial-value: 50%;
}

@include stage($stage-ink);

.spot {
  position: relative;
  isolation: isolate;
  overflow: hidden;
  border: 0;
  cursor: pointer;
  padding: $sp-5 $sp-10;
  border-radius: $r-pill;
  background: rgba($subject-cream, .10);
  box-shadow: inset 0 0 0 1px rgba($subject-cream, .30);
  color: $subject-cream;
  font-family: inherit;
  font-size: clamp(16px, 5vw, 20px);
  font-weight: 700;
}

.spot::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  background: radial-gradient(circle 96px at var(--mx) 50%, rgba($color, .95), rgba($color, 0) 72%);
}

.spot__label { position: relative; }

.spot.is-demo { animation: spot-sweep $duration $easing infinite; }

// 8% → 92% → 8% 로 되돌아와 끝난다. 92% 에서 끊고 처음으로 점프하면 빛이 순간이동한다
@keyframes spot-sweep {
  0%   { --mx: 8%; }
  50%  { --mx: 92%; }
  100% { --mx: 8%; }
}

@media (prefers-reduced-motion: reduce) {
  .spot.is-demo { animation: none; }
  .spot::before { background: radial-gradient(circle 96px at 50% 50%, rgba($color, .95), rgba($color, 0) 72%); }
}

@property --mx {
  syntax: "<percentage>";
  inherits: true;
  initial-value: 50%;
}
html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.spot {
  position: relative;
  isolation: isolate;
  overflow: hidden;
  border: 0;
  cursor: pointer;
  padding: 20px 40px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.1);
  box-shadow: inset 0 0 0 1px rgba(255, 247, 230, 0.3);
  color: #fff7e6;
  font-family: inherit;
  font-size: clamp(16px, 5vw, 20px);
  font-weight: 700;
}

.spot::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  background: radial-gradient(circle 96px at var(--mx) 50%, rgba(47, 109, 246, 0.95), rgba(47, 109, 246, 0) 72%);
}

.spot__label {
  position: relative;
}

.spot.is-demo {
  animation: spot-sweep 2s ease-out infinite;
}

@keyframes spot-sweep {
  0% {
    --mx: 8%;
  }
  50% {
    --mx: 92%;
  }
  100% {
    --mx: 8%;
  }
}
@media (prefers-reduced-motion: reduce) {
  .spot.is-demo {
    animation: none;
  }
  .spot::before {
    background: radial-gradient(circle 96px at 50% 50%, rgba(47, 109, 246, 0.95), rgba(47, 109, 246, 0) 72%);
  }
}

// 실제 동작: 커서가 버튼 위에 오면 빛의 중심(--mx)이 커서를 따라가고, 손을 떼면 데모 루프로 돌아간다.
var spot = document.querySelector('.spot');
spot.addEventListener('pointermove', function (e) {
  var r = spot.getBoundingClientRect();
  spot.classList.remove('is-demo');
  spot.style.setProperty('--mx', ((e.clientX - r.left) / r.width * 100) + '%');
});
spot.addEventListener('pointerleave', function () {
  spot.style.removeProperty('--mx');
  spot.classList.add('is-demo');
});

import { useState } from "react";
import type { CSSProperties, PointerEvent } from "react";
import styles from "./SpotlightButton.module.scss";

export type SpotlightButtonProps = {
  label?: string;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string; "--mx"?: string };

export default function SpotlightButton({
  label = "See pricing",
  duration = 2000,
  easing = "ease-out",
  color = "#2f6df6",
}: SpotlightButtonProps) {
  const [mx, setMx] = useState<string | null>(null);

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  if (mx) { vars["--mx"] = mx; }

  function move(e: PointerEvent<HTMLButtonElement>) {
    const r = e.currentTarget.getBoundingClientRect();
    setMx(`${((e.clientX - r.left) / r.width) * 100}%`);
  }

  return (
    <button
      type="button"
      className={`${styles.spot} ${mx ? "" : styles.loop}`}
      style={vars}
      onPointerMove={move}
      onPointerLeave={() => setMx(null)}
    >
      <span className={styles.label}>{label}</span>
    </button>
  );
}